Hitherto, shafts have been sealed by means of conventional stuffing boxes, including mechanical packings consisting of annular gaskets compressed by annular gland followers moved axially against the packing, thereby converting axial force to radial components of force. A large proportion of the axial force is consumed in compression of the mechanical packing. Mechanical packing takes the shape of the restraining container and is subjected to deformation due to eccentric rotation of the shaft. The resulting phenomena is termed "pumping the seal."
The second generation in development of conventional stuffing boxes included pressurized diaphragms having an independent source of fluid pressure, usually fluid from the discharge side of a pump or an air compressor. These diaphragm seals proved unsatisfactory for several reasons: sealing pressure failed during power failures; temperature tended to build up due to frictional heat causing the enclosed fluid to expand in an uncontrollable manner; the mechanical arrangement of the seals did not permit flushing or lubrication of the shaft at the packing interface.
In contrast to prior art relating to shaft sealing devices, the present invention provides means for applying direct radial force to mechanical packing by compressing the fluid in a hermetically sealed, self-contained elastomeric ring by converting mechanically applied axial pressure to hydraulic pressure by deforming the ring. The eccentric motion of a rotating shaft is then compensated for by relocation of the fluid within the elastomeric ring. A self-centering sealing means is thus provided.
The present invention incorporates this feature to provide uniform sealing pressures to multiple compartments in a single seal cartridge.
The number of compartments required in a single seal is related to the operating pressure of the apparatus or machine to which it is attached.
An indirect, non-wetting cooling means is provided for simultaneously cooling the mechanical packing and the elastomeric ring adjacent to the cooling means.